Fluoroelastomer curing process with phosphonium compound

ABSTRACT

A fluoroelastomer composition curable in reactive admixture with an acid acceptor that includes an elastomeric gum consisting essentially of vinylidene fluoride, tetrafluoroethylene, and copolymerizable hydrocarbon olefin and a combination of 
     (A) polyhydroxy compound, and 
     (B) organo-onium compound, 
     and process of curing the elastomeric copolymer with an admixture of (A) and (B) and an acid acceptor, and the resulting shaped or formed, cured articles are described.

This is a division of application Ser. No. 311,135 filed Feb. 15, 1989,now U.S. Pat. No. 4,882,390 which is a continuation-in-part ofapplication Ser. No. 176,410 filed Apr. 1, 1988 now abandoned.

This invention relates to fluoroelastomer compositions comprising anelastomeric copolymer of tetrafluoroethylene vinylidene fluoride, andone or more hydrocarbon olefins and curing agent. In another aspect, itrelates o a process for curing the shaped or formed articles of suchfluoroelastomer composition and the resulting shaped or formed, curedarticles.

Various vinylidene fluoride, tetrafluoroethylene and propylenecopolymers and a number of curing systems therefor, have been describedin the art. However, for some of such copolymers the curing systemscontaining polyhydroxy and organo-onium compounds have been described asinferior for thee copolymers, e.g. see European Pat. Application No.218929 A2 (Yasumichi et al.). In a comparative example, Yasumichi et al.describe the cure properties of one such copolymer withbenzyltriphenylphosphonium chloride and bisphenol AF as a poor cure andnot suitable for practical application. Consistent with this finding,various alternative cure systems for these copolymers have beenproposed; for example, U.S. Pat. No. 3,859,259 (Harrell) discloses theuse of diamines and diamine carbamates as crosslinking agents and acompound able to accelerate the crosslinking reaction selected from thegroup: quaternary ammonium compounds, quaternary phosphonium compounds,penta-substituted guanidines and salts thereof, tri-substitutedamidines, cyclic polyethers and open-chain polyethers. And Jap. KokaiPat. Application No. Sho 52[1977]-41662 discloses the use of a peroxycompound as the crosslinking agent and a crosslinking promoter.

Ethylenically unsaturated copolymers derived from vinylidene fluoride,tetrafluoroethylene, and propylene by treatment with an aqueous alkalinesolution containing an onium compound to introduce ethylenicunsaturation before curing have been proposed, e.g. see U.S. Pat. No.4,645,799 (Wachi et al.) and said European Pat. Application No. 218929A2 (Yasumichi et al.). Wachi et al. disclose the use of an organicperoxide and a vulcanization accelerator, e.g. allyl compounds, as thecuring system. Yasumichi et al. disclose the use of a polyhydroxycompound and a vulcanization accelerator, e g. a quaternary ammoniumcompound, as the curing system.

Yasumichi et al.'s finding of poor cure for said comparative example isnot inconsistent with W. W. Schmiegel's studies indicating theimportance of the presence of hexafluoropropylene monomers in achievinga useful state of cure when crosslinking with nucleophilic crosslinkingagents, see W. W. Schmiegel, "Cross-linking of VinylideneFluoride/Hexafluoropropylene Fluoroelastomer by Bisphenols," Kautschuk +Gummi Kunststoffe, 31/3 (1978), pp. 137-148, and W. W. Schmiegel, DieAngewandte Makromolekulare Chemie, "Crosslinking of ElastomericVinyliden Fluoride Copolymers with Nucleophiles", 76/77 (1979), pp.39-65. Schmiegel concludes that vinylidene fluoride copolymers that donot contain hexafluoropropylene are less sensitive to attack bynucleophiles, such as bisphenol compounds, than copolymers containinghexafluoropropylene. However, Jap. Kokoku Pat. Nos. Sho 60[1985]-19324(Hisasue et al.) and Sho 60[1985]-19325 (Hisasue et al.) state thatcopolymers comprising 30 to 90 mole percent vinylidene fluoride, 5 to 50mole percent ethylene tetrafluoride (sic. tetrafluoroethylene), and 5 to40 mole percent propylene and those comprising 10 to 30 mole percentvinylidene fluoride, 25 to 50 mole percent ethylene tetrafluoride (sic.tetrafluoroethylene) and 25 to 45 mole percent propylene can becrosslinked using various techniques including inter alia nucleophilicagents (e.g., hydroquinone, catechol, Bisphenol A) either alone or incombination with polyethers. However, neither patent discloses byworking example or otherwise that such nucleophilic reagents were everin fact used to cure the copolymer and such disclosure appearsinconsistent with Yasumichi et al. and Schmiegel's teachings.

Cure systems for tetrafluoroethylene and propylene copolymers have alsobeen described, e.g., U.S. Pat. Nos. 3,892,641 (Tabata et al.),4,277,586 (Ukihashi et al.), describe high energy ionizing radiation andperoxy cure systems and U.S. Pat. No. 4,148,982 (Morozumi et al.)mention the use of polyhydroxy aromatic compounds for vulcanization ofthe copolymer only after thermal modification of the copolymer.

This invention provides a elastomeric composition comprising saturatedelastomer gum consisting or consisting essentially of interpolymerizedunits derived from vinylidene fluoride, tetrafluoroethylene, andcopolymerizable hydrocarbon olefin, e.g. propylene, and the combinationof

(A) polyhydroxy compound, and

(B) organo-onium compound, such as those selected from the groupconsisting of ammonium, arsonium, phosphonium, stibonium,amino-phosphonium, phosphorane (e.g., triarylphosphorane), iminium, andsulfonium compounds.

However, if said gum is derived from vinylidene fluoride,tetrafluorethylene, and olefin, such as propylene, and said polyhydroxycompound is bisphenol AF (i.e., hexafluoroisopropylidene-bis(4-hydroxybenzene)) and said organo-onium compound is a phosphoniumcompound, it is other than benzyltriphenylphosphonium chloride.

In order to cure the elastomeric composition, said composition can beadmixed with acid acceptor, e.g. a conventional acid acceptor likecalcium hydroxide, to render the composition curable. The invention alsoprovides a process of curing shaped or formed articles, e.g. O-rings,which process comprises providing a mixture of the gum, component A (thepolyhydroxy compound), and component B (the organo-onium compound), andacid acceptor, and shaping and curing curing the resulting mixture.Preferred compositions additionally include one or more diorgano sulfuroxide compounds. The invention further provides shaped or formedarticles comprising said cured copolymers.

The novel cure system of this invention provides surprisingly usefulstate of cure and synergistic cure rates for vinylidene fluoride,tetrafluoroethylene, and hydrocarbon olefin copolymers using a curesystem of polyhydroxy and organo-onium compounds without requiringhexafluoropropylene comonomers or pretreatments, such as those describedin the art cited above.

The copolymers used in this invention are saturated (i.e. essentiallyfree of unsaturation), fluorine-containing, elastomeric gums consistingor consisting essentially of interpolymerized units derived fromvinylidene fluoride, tetrafluoroethylene and one or more, preferably oneor two, copolymerizable hydrocarbon olefin monomers. The olefin monomerscan be represented, for example, by those having the formula R¹ R¹ C═CR¹R¹ wherein R¹ groups can be the same or different and can be selectedfrom hydrogen, alkenyl, and alkyl, can be straight chain or branched,with preferably one to three carbon atoms. Representative examples ofolefin monomers are ethylene, propylene, isobutylene, butene-1,butene-2, and 1,3-butadiene. The molar ratios of said monomers used inmaking the copolymer will be selected to achieve the physical properties(e.g., chemical resistance, high temperature stability, low temperatureflexibility, and fuel resistance desired in the cured polymer. Theselection of such ratios will be within the skill of the art, based onthe known relationships between the relative amounts of particularmonomers and the physical properties of the copolymer. Generally,however, the copolymers to be used in this invention are thosecomprising about 2 to 90 mole percent vinylidene fluoride, 5 to 65 molepercent tetrafluoroethylene, and 5 to 45 mole percent hydrocarbonolefin. A particularly useful class of copolymers are those comprisingabout 2 to 65 mole percent of vinylidene fluoride, 20-60 mole percent oftetrafluoroethylene, and 10-50 mole percent hydrocarbon olefin.Preferably, the hydrocarbon olefin is propylene. The copolymers of thisinvention are inclusive of those known in the art and can be prepared byknown techniques such as those described in U.S. Pat. No. 3,859,259,Jap. Pat. No. Sho 60[1985]-19324, Jap. Pat. No. Sho 60[1985]-19325.

The polyhydroxy compound which is admixed with the copolymer is onecapable of functioning as a crosslinking agent for the copolymer. Suchagents are well-known and are described in the art, e.g., U.S. Pat. Nos.4,259,463 (Moggi et al.), 3,876,654 (Pattison), and 4,233,421 (Worm),and can include aromatic polyhydroxy compounds and aliphatic polyhydroxycompounds, and the derivatives of said compounds. Also, blends ofpolyhydroxy compounds may be used in this invention.

Representative aromatic, polyhydroxy compounds include the following:di-, tri-, and tetrahydroxy-benzenes, naphthalenes, and anthracenes, andbisphenols of the formula ##STR1## wherein A is a divalent aliphatic,cycloaliphatic, or aromatic radical of 1 to 13 carbon atoms, or a thio,oxy, carbonyl, sulfinyl, or sulfonyl radical; A is optionallysubstituted with one or more chlorine or fluorine atoms; x is 0 or 1; nis 1 or 2; and any aromatic ring of the polyhydroxyl compound can beoptionally substituted with at least one atom of chlorine, fluorine, orbromine, or carboxyl, or an alkyl, or an acyl (e.g., a --COR where R isa C₁ to C₈ alkyl, aryl, or cycloalkyl group) radical. It will beunderstood from the above bisphenol formula that the --OH groups can beattached in any position (other than number one, i.e., the carbon atomswhere the A group is attached to the rings) in either ring. Specificaromatic polyhydroxy compounds include 4,4,'-thiodiphenol,isopropylidene-bis(4-hydroxybenzene) (i.e. bisphenol A),hexafluoroisopropylidene-bis(4-hydroxybenzene), (i.e. bisphenol AF) andare described or illustrated in U.S. Pat. No. 4,233,421 (Worm) all ofwhich teachings are incorporated herein by reference.

Representative aliphatic polyhydroxy compounds include fluoroaliphaticdiols, e.g. 1,1,6,6-tetrahydrooctafluorohexanediol, and others such asthose described in U.S. Pat. No. 4,358,559 (Holcomb et al.) andreferences cited therein. Representative polyhydroxy derivatives ofpolyhydroxy compounds which can be used as crosslinking agents aredescribed in U.S. Pat. No. 4,446,270 (Guenthner et al.), and include,for example, 2-(4-allyloxypenyl)-2-(4-hydroxyphenyl) propane.

Preferred polyhydroxy compounds are aromatic polyhydroxy compoundshaving formula (I) such as bisphenol A and bisphenol AF. A blend of twoor more of the polyhydroxy compounds can be used in this invention. Whenchanging from one polyhydroxy compound to another in a givencomposition, one skilled in the art will be able to select a curing timeand temperature that will give a suitable rate of cure for a particularapplication.

The organo-onium compound which is admixed with the copolymer is capableof functioning as a vulcanization accelerator. As is known, anorgano-onium compound is the conjugate acid of a Lewis base (e.g.,phosphine, amine, ether, or sulfide) and can be formed by reacting saidLewis base with a suitable alkylating agent (e.g., an alkyl halide oracyl halide) resulting in the expansion of the valence of the electrondonating atom of the Lewis base and a positive charge on theorgano-onium compound. Many of the organo-onium compounds useful in thisinvention contain at least one heteroatom, i.e., a non-carbon atom suchas N, P, S, O, bonded to organic or inorganic moieties. The organo-oniumcompounds suitable for use in this invention are known and are describedin the art. See, for example, U.S. Pat. No. 3,655,727 (Patel et al.),U.S. Pat. No. 3,712,877 (Patel et al.), U.S. Pat. No. 3,857,807(Kometani), U.S. Pat. No. 3,686,143 (Bowman), U.S. Pat. No. 3,933,732(Schmiegel), U.S. Pat. No. 3,876,654 (Pattison), U.S. Pat. No. 4,233,421(Worm), and U.S. Pat. No. 4,259,463 (Moggi et al.), European PatentApplication No. 0182299A2 and European Patent Application No. 0120462A1;and also see West, A. C. and Holcomb, A. G. "Fluorinated Elastomers",Kirk-Othmer; Encyclopedia of Chemical Technology, Vol. 8, 3rd Ed., JohnWiley & Sons, Inc., pp. 500-515 (1979). Mixtures of organo-oniumcompounds are also useful in this invention. Said organo-onium compoundsinclude quaternary organo-onium compounds, such as those selected fromthe group consisting of ammonium, arsonium, phosphonium, stibonium,amino-phosphonium, phosphorane (e.g., triarylphosphorane), and iminiumcompounds, and sulfonium compounds. One class of quaternary organo-oniumcompounds are organic compounds ionically associated with an anion,wherein at least one nitrogen, phosphorus, arsenic or antimony atom iscovalently bonded to four organic moieties. In another class ofquaternary organo-onium compounds the nitrogen, phosphorus, arsenic orantimony atom may be a heteroatom in a cyclic structure, e.g.,8-benzyl-1,8-diazobicyclo[5,4,0]-7-undecenium chloride. One class ofquaternary organo-onium compounds herein broadly comprises relativelypositive and relatively negative ions (the phosphorus, arsenic, antimonyor nitrogen atom generally comprising the central atom of the positiveion), these compounds being generally known as ammonium, phosphonium,arsonium, or stibonium salts or compounds preferably having the generalformula: ##STR2## where Q is selected from the group consisting ofnitrogen, phosphorous, arsenic, and antimony; X is an organic orinorganic anion (e.g. halide, sulfate, acetate, phosphate, phosphonate,hydroxide, alkoxide, phenoxide, bisphenoxide, etc.); n is equal to thevalence of the anion X; and R², R³, R⁴, and R⁵ are selected from thegroup of radicals consisting of alkyl, aryl, alkenyl, or combinationsthereof. R², R³, R⁴ and R⁵ can be substituted with chlorine, fluorine,bromine, cyano, --OR, and --COOR moieties where R is selected from thegroup consisting of C₁ to C₂₀ alkyl, aryl, aralkyl, and alkenyl. Anypair of said R groups can be connected with each other and the Q atom toform a heterocyclic ring. However, compositions wherein said copolymeris derived from vinylidene fluoride, tetrafluoroethylene and propylenemonomer, and the polyhydroxy compound is bisphenol AF, Q is phosphorous,X is a chloride anion, n is 1, three of the groups, R², R³, R⁴, and R⁵are phenyl moieties, the remaining R group cannot be a benzyl moiety. Apreferred class of quaternary organo-onium compounds has the generalformula (II) and at least one of the groups R², R³, R⁴ or R⁵ is alkyl,or alkenyl. Representative of this preferred class aretetrabutylammonium chloride, tetrabutylammonium bromide,tetrahexylammonium chloride, tetraheptylammonium chloride,tetrapentylammonium chloride, tributylallylihosphonium chloride,tributylbenzylphosphonium chloride, dibutyldiphenylphosphonium chloride,tetrabutylphosphonium chloride and tributyl(2-methoxy)propylphosphoniumchloride compounds. Said tributyl(2-methoxy)propylphosphonium chlorideis believed to be novel.

Another class of quaternary organo-onium compounds useful in thisinvention are amino-phosphonium compounds some of which are described inthe art, see for example, U.S. Pat. No. 4,259,463 (Moggi et al.). Theamino-phosphonium compounds can be of the ionic type described by Moggiet al. and can have the general formulas

    [P(NR.sup.6 R.sup.7).sub.n R.sup.8.sub.4-n ].sub.m.sup.+ Y.sup.-m (III)

or

    R.sup.9 [P(NR.sup.6 R.sup.7).sub.r R.sup.8.sub.3-r ].sub.2.sup.+ pY.sup.-m (IV)

Where R⁶, R⁷, and R⁸ can be the same or different, and may be selectedfrom the group consisting of alkyl, cycloalkyl, aryl, aralkyl, oxyalkylor poly(oxyalkyl) groups with a free or etherified terminal OH function,may contain from 1 to 18, but preferably from 1 to 12 carbon atoms andmay contain, as substituents, halogens CN, OH, carboalkoxy groups;moreover, R⁶ and R⁷ may be connected with each other to form with thenitrogen atom a heterocyclic ring. R⁹ is a bivalent alkylene, arylene oroxyalkylene radical, n is a whole number between 1 and 4, r is a wholenumber between 1 and 3, m is a whole number between 1 and 3 andcorresponds to the valence of anion Y, p is a coefficient, such that mtimes p is 2. Y is an anion of valency m and may be either organic orinorganic. Examples of such anions are halide, perchlorate, nitrate,tetrafluoroborate, hexafluorophosphate, oxalate, acetate, stearate,haloacetate, para-toluensulphonate phenoxide and bisphenoxide andhydroxy anions. Y may also be a complex anion such as ZnCl₄ ⁻², CdCl₄⁻², NiBr₄ ⁻², HgI₃ ⁻¹. A particularly preferred amino-phosphoniumaccelerator is benzyltris(dimethylamino)phosphonium chloride.

Another class of quaternary organo-onium compounds useful in thisinvention are phosphorane compounds such as triarylphosphoranecompounds; some of the latter compounds are known and are described inthe art, see for example, U.S. Pat. No. 3,752,787 (de Brunner), whichdescriptions are herein incorporated by reference. Some of thetriarylphosphorane compounds useful in this invention have the generalformula ##STR3## wherein Ar is aryl, selected for example, from phenyl,substituted phenyl e.g. methoxyphenyl, chlorophenyl, tolyl, and otherknown aryl groups, e.g. naphthyl. R¹⁰ and R¹¹ are selected from thegroup consisting of (1) separate groups selected individually from (a)hydrogen, methyl, ethyl, propyl, and carbalkoxy (C₁ -C₆ alkyl) in thecase of R¹⁰, and b) carbalkoxy (C₁ -C₆ alkyl), cyano, and --CONH₂ in thecase of R¹¹ ; and (2) a single group which together with the carbon atomto which the single group is attached form a cyclic group selected from##STR4##

Another class of quaternary organo-onium compounds useful in thisinvention are iminium compounds. Some of the iminium compounds useful inthis invention are organic compounds having the general formula ##STR5##wherein R¹² is a monovalent organic radical terminated with a non-carbonatom such as P, S, O, or N, such that said organic radical is covalentlybonded to the nitrogen atom through said non-carbon atom, c is thevalence of the anion X, e.g., 1 or 2, and X is an organic or inorganicanion, e.g., halide, hydroxy, sulfate, thiosulfate, nitrate, formate,acetate, cyanate, thiocyanate, tetraphenylborate,2-mercaptobenzothiazolate, phosphate, phosphonate, alkoxide, phenoxide,bisphenoxide or perchlorate ions. The positive charge of the cation canbe assigned to the N atom, but it can also equally be distributed to thetwo non-carbon atoms.

Another class iminium compounds useful in this invention are known anddescribed in the art, e.g., European Patent Applications Nos. 182299A2and 120462A1, which descriptions are herein incorporated by reference.Some of said iminium compounds have the general formula ##STR6## whereinR¹³, R¹⁴ and R¹⁵ can be the same or different and can be selected fromthe group consisting of aryl, C₁ to C₂₀ alkyl, C₃ to C₈ cycloalkyl, C₇to C₂₀ aralkyl groups. Said aryl or aralkyl groups can, optionally, besubstituted with one or more groups selected from the group consistingof C₁ to C₁₀ alkyl groups, C₃ to C₈ cyclo-alkyl groups, halogen atomsand groups having the formula ##STR7## where R¹⁶ and R¹⁷ are the same ordifferent and are selected from the group consisting of C₁ to C₂₀ alkyl,a C₃ to C₈ atom cycloalkyl and phenyl groups. X is an anion such asthose described above and c is the valence of X.

Representative quaternary organo-onium compounds includephenyltrimethylammonium chloride, tetrapentylammonium chloride,tetrapropylammonium bromide, tetrahexylammonim chloride,tetraheptylammonium bromide, tetramethylphosphonium chloride,tetramethylammonium chloride, tetrabutylphosphonium chloride,tributylbenzyl phosphonium chloride, tetrabutylammonium chloride,tetrabutylammonium bromide, tributylallylphosphonium chloride,tetraphenylphosphonium chloride, tetraphenylarsonium chloride,tetraphenylstibonium chloride,8-benzyl-1,8-diazobicyclo[5.4.0]7-undecenium chloride,benzyltris(dimethylamino)phosphonium chloride, andbis(benzyldiphenylphosphine)iminium chloride.

Sulfonium compounds useful in this invention are known and described inthe art, e.g., see U.S. Pat. No. 4,233,421 (Worm). Briefly described, asulfonium compound is a sulfur-containing organic compound in which atleast one sulfur atom is covalently bonded to three organic moietieshaving from 1 to 20 carbon atoms by means of carbon-sulfur covalentbonds and is ionically associated with an anion. Said organic moietiescan be the same or different. The sulfonium compounds may have more thanone relatively positive sulfur atom, e.g. [(C₆ H₅)₂ S⁺ (CH₂)₄ S⁺ (C₆H₅)₂ ]2Cl⁻, and two of the carbon-sulfur covalent bonds may be betweenthe carbon atoms of a divalent organic moiety, i.e., the sulfur atom maybe a heteroatom in a cyclic structure.

A preferred class of sulfonium compounds are salts having the formula##STR8## wherein R¹⁸, R¹⁹, and R²⁰ can be the same or different,provided that at least one of such groups is aromatic, and such groupscan be selected from aromatic radicals having 4 to 20 carbon atoms(e.g., substituted and unsubstituted phenyl, thienyl, and furanyl) andalkyl radicals having 1 to 20 carbon atoms. The alkyl radicals includesubstituted alkyl radicals (for example, substitutents such as halogen,hydroxy, alkoxy, aryl. Z is selected from the group consisting ofoxygen; sulfur; >S═O; >C═O; ##STR9## where R²¹ is aryl or acyl (such asacetyl, benzoyl, etc.); a carbon-to-carbon bond; or ##STR10## where R²²and R²³ are selected from the group consisting of hydrogen, alkylradicals having 1 to 4 carbon atoms, and alkenyl radicals having 2 to 4carbon atoms; and n is zero or 1; X is an inorganic or organic anion;and a is the valence of X. Suitable representative anions includehalide, e.g. chloride add bromide, sulfate, bisulfate, nitrate,hydroxide, perchlorate, trifluoromethane sulfonate, acetate, benzenesulfonate, tetrafluoroborate, hexachlorophosphate, hexafluorophosphate,hexachlorostannate, hexafluoroarsenate, hexafluoroantimonate, phenoxideand bisphenoxide.

A further component in the composition is an acid acceptor. Acidacceptors can be inorganic or organic compounds. Organic acid acceptorsinclude sodium stearate, and magnesium oxalate. However, acid acceptorsare generally inorganic bases an include magnesium oxide, lead oxide,calcium oxide, calcium hydroxide, dibasic lead phosphite, zinc oxide,barium carbonate, strontium hydroxide, calcium carbonate, etc. Thepreferred acid acceptors are magnesium oxide and calcium hydroxide. Theacid acceptors can be used singly or in combination and preferably areused in amounts ranging from 2 to 25 parts per 100 parts by weight ofthe polymer.

Highly preferred compositions contain one or more diorgano sulfur oxidecompounds. Said diorgano compounds, when compounded with the otheringredients in the composition can function to increase the cure rate ofthe composition. Said diorgano compounds are known in the art and aredescribed, for example, in U.S. Pat. No. 4,287,320 (Kolb). Saidcompounds, briefly described, contain at least one sulfur atom, one ortwo oxygen atoms bonded only to each said sulfur, and, additionally, twoneutral organic radicals which bond directly to the sulfur atoms bysingle C-S bonds, and have the general formula (R²⁴)₂ SO_(x) wherein xis 1 or 2, and each R²⁴ is an organic radical. Each organic radical,R²⁴, may be the same or different and each radical may contain from oneto twenty or more carbon atoms, although one to about eight carbon atomsare preferred, with a total of not more than about thirty carbon atomsassociated with each sulfur atom. The two R²⁴ groups together may be asingle alkylene group, forming with the sulfur atom a heterocyclic ring.The carbon skeletal chain of the R²⁴ groups may be linear, branched, orcyclic, may be aliphatic or aromatic, and may contain catenary heteroatoms, such as oxygen, in addition to carbon. Said chain may besubstituted with, e.g., halide, alkoxy, --SOR, --SO₂ R, carbalkoxy, oxo,hydroxyl, nitro, cyano, alkyl, aryl, or it may be unsubstituted. Suchcompounds include diorgano sulfoxides, (R²⁴)₂ SO, and diorgano sulfones,(R²⁴)₂ SO₂, and are described, for example in Basic Principles ofOrganic Chemistry, Roberts and Caserio, W.A. Benjamin Company, N.Y.,N.Y., 1965, particularly pages 756-760, and Organic Syntheses, Vol. 1,pages 718-725, Vol. II, pages 1709-1715, Reinhold Publishing Co., N.Y.,N.Y., 1957. Representative diorgano sulfur oxides includedimethylsulfone, tetramethylene sulfone, and bis(4-chlorophenyl)sulfone. Additional diorgano sulfur oxides are described in U.S. Pat.No. 4,287,320 (Kolb) which teachings are incorporated herein byreference.

Fillers are often added to the polymers discussed above to improve themolding characteristics and other properties. When a filler is employedit is added to the vulcanization recipe in amounts of up to about 100parts per hundred parts by weight of rubber, preferably between about 15and 50 parts per hundred parts by weight of the rubber. Examples offillers which may be used are reinforcing thermal grade carbon blacks ornon-black pigments of relatively low reinforcement characteristics suchas clays, barytes, etc.

The organo-onium compound and polyhydroxy compound can be introduced tothe curable copolymer in the form of finely divided solids by millingsaid compounds into the copolymer gum stock. Thus mixed, the gum stockcan generally be stored at room temperature for extended periods, e.g.,up to two years or more. Prior to curing, an acid acceptor is milledinto the organo-onium-polyhydroxy-containing gum stock, after which thestorage life of the stock is more limited. Of course, all of thecomponents of the curing system may be admixed prior to theirincorporation into the elastomer without departing from the scope ofthis invention. Another method of introducing the components of thisinvention into the curable copolymer can include making a complex of themetal salt, e.g., sodium, calcium, etc., of the polyhydroxy compound anorgano-onium compound and adding said complex along with any additional,if desired, polyhydroxy compound to the unvulcanized copolymer. Saidmetal salt can be made by reacting the polyhydroxy compound with a base,e.g. sodium methoxide, in a suitable solvent, e.g. methanol. In someinstances it may also be desirable to add one or more diorgano sulfuroxide compounds, and other conventional adjuvants or ingredients, e.g.retarding agents, processing aids, reinforcing agents, and fillers, tothe gum stock.

The relative amounts of said polyhydroxy and organo-onium compounds arepresent in the composition in such amounts as to provide the desiredcure of the composition when mixed with acid acceptor. Representativeproportions of components of the curing system are set forth below inTable I. All amounts referred to therein are in parts per 100 parts byweight rubber abbreviated "phr" or in millimoles per hundred partsrubber abbreviated "mmhr", unless otherwise indicated, the "rubber"means the elastomer copolymer or gum. These proportions are generalranges and the particular amount for each particular cure time andtemperature will become apparent to those skilled in the art.

                  TABLE I                                                         ______________________________________                                        Formulation Ranges                                                            Component             Amounts                                                 ______________________________________                                        Acid acceptor         0.5 to 40 phr                                           Organo-onium compound 0.2 to 10 mmhr                                          Polyhydroxy compound  0.3 to 10 mmhr                                          ______________________________________                                    

Preferred compositions contain diorgano sulfur oxide compound mostpreferably tetramethylene sulfone, in a concentration range of 0.01 to 5phr. Useful elastomers are obtained within the aforementionedformulation limits, although elastomeric products having particularlydesired properties may be obtained by varying the relative amounts ofthe components within the specified ranges. Preferably, compositionscomprise 2.3 to 3.0 mmhr organo-onium compound and 3.5 to 6.0 mmhrpolyhydroxy compound.

Most preferably, said organo-onium compound and said polyhydroxycompound are introduced to the composition in the form of a complex,derived from said organo-onium compound and said polyhydroxy compound.Said complex is generally prepared by combining in reactive admixtureequimolar amounts of sodium methoxide and polyhydroxy compound in asuitable solvent (e.g., methanol) to form the monosodium salt of thepolyhydroxy compound. The resulting mixture is then reacted with anequimolar quantity of organo-onium compound to form a complex of thepolyhydroxy compound and organo-onium compound.

In accordance with this invention, the desired amount of acid acceptor,organo-onium compound and polyhydroxy compound, diorgano sulfur oxidecompounds, if any, and other conventional adjuvants or ingredients areadded to the unvulcanized copolymer (i.e., gum stock) and intimatelyadmixed therewith or compounded by employing any of the usual rubbermixing devices such as Banbury mixers, roll mills, or any otherconvenient mixing device.

For best results the temperature of the mixture on the mill should notrise above about 120° C. During milling it is necessary to distributethe components and adjuvants uniformly throughout the curable polymer.The curing process typically comprises extrusion or pressing thecompounded mixture in a mold e.g., a cavity or a transfer mold, andsubsequent oven curing. Pressing of the compounded mixture (press cure)is conducted at a temperature between about 95° C. and about 230° C.,preferably between about 150° C. and about 205° C. for a period of from1 minute to about 15 hours, usually from 5 minutes to 30 minutes. Apressure of between about 700 kPa and about 20,600 kPa, preferablybetween about 3,400 kPa and about 6,800 kPa is imposed on the compoundedmixture in the mold. The molds first may be coated with a release agent,such as a silicone oil, and prebaked. The molded vulcanizate is thenusually post cured (oven cured) at a temperature between about 150° C.and about 315° C., usually at about 232° C. for a period of from about 2hours to 50 hours or more depending on the cross-sectional thickness ofthe sample. For thick sections, the temperature during the post cure isusually raised gradually from the lower limit of the range to thedesired maximum temperature selected. For thinner cross-sections, e.g.,less than 5 mm, the vulcanizate or cured sheet section may be put intothe oven at the desired maximum temperature. The maximum temperatureused is preferably about 232° C. and is held at this value for about 4hours or more.

One major utility of the vulcanized, highly fluorinated elastomers ofthis invention lies in their use as shaft seals in automotiveapplications, gaskets, O-rings and the like, for containing fluids underpressure at elevated temperatures, as, for example, in hydraulic systemsin aircraft, or as components of reactors in the processing ofchemicals.

The following examples are offered to aid in a better understanding ofthe present invention and are not to be unnecessarily construed aslimiting the scope thereof.

EXAMPLES

In the examples, indicated results were obtained using the followingtest methods:

Mooney Viscosity ASTM D1646-81

Cure Rheology Tests were run on uncured, compounded admixture using theOscillating Disk Rheometer (ODR) Model 100S Monsanto in accordance withASTM D 2084-82 with a micro die, no preheat, an oscillator frequency of100 cpm and a 3° arc. Minimum torque (M_(L)) and highest torque attainedduring specified period of time when no plateau or maximum torque isobtained (M_(H)) were reported. Also reported were t_(s) 0.2 (time fortorque to increase 0.2 N.m above M_(L)), t'50 [time for torque to reachM_(L) +0.5 (M_(H) -M_(L))], and t'90 [time for torque to reach M_(L)+0.9(M_(H) -M_(L))].

Press Cure Unless otherwise noted, 150×150×1.8 mm sheets were preparedfor physical property determination by pressing at about 6.9×10³ kPa for15 min. at 177° C.

Post Cure Samples were removed rom the press and placed in a circulatingair oven. The oven was maintained at 230° C. for 16 hours.

Tensile Strength at Break--ASTM D 412-75 on a sample

Elongation at Break--cut from 1.8 mm sheet with

Modulus at 100% Elongation--ASTM Die D.

Hardness ASTM D 2240-85 Method A. Type A-2 shore Durometer was used.

Mooney Scorch Tests were run on uncured, compounded formulations using aScott Testing Inc. Mooney Viscometer Model ST1, in accordance with ASTMD1646-81 with a 1 minute preheat and a small rotor at 121° C.

In the following examples, the fluoroelastomer gums listed in Table IIwere used.

                  TABLE II                                                        ______________________________________                                        Flu-                                                                          oro-                                                                          elas-            Composition                                                  tomer Mooney     (mole %)                                                     gum   viscosity  CF.sub.2 ═CH.sub.2                                                                  CF.sub.2 ═CF.sub.2                                                                CH.sub.3 CH═CH.sub.2                   ______________________________________                                        A     51 @ 121° C.                                                                      32        41      27                                         B     74 @ 150° C.                                                                      36        45      19                                         C     41 @ 121° C.                                                                      36        42      22                                         D     62 @ 121° C.                                                                      30        42      28                                         ______________________________________                                    

Said fluoroelastomer gums were prepared according to the methoddescribed in U.S. Pat. No. 3,859,259 (Harrell et al.), and JapaneseKokoku Pat. No. Sho 38[1963]-21239.

The organo-onium accelerators were either obtained from commercialsources or made according to known methods. Tetraphenylphosphoniumchloride and tetrabutylphosphonium chloride were obtained from AldrichChemical Company. 8-Benzyl-1,8-diazobicyclo[5.4.0]7-undecenium chloridewas made according to the procedure described in U.S. Pat. No.3,857,807, benzyltris(dimethylamino)phosphonium chloride was madeaccording to the procedure cited in U.S. Pat. No. 4,259,463 (Moggi etal.), i.e. U.S. Pat. No. 2,703,814, (Dye). Tetrabutylphosphoniumchloride, tributylbenzylphosphonium chloride, dibutyldiphenylphosphoniumchloride, were made according to procedures described in referencescited in U.S. Pat. No. 3,876,654 (Pattison).Tributyl(2-methoxy)propylphosphonium is prepared by reactingtributylphosphine and allylchloride in methanol at 60° to 80° C. or 6 to8 hours. Ammonium compounds were obtained from Aldrich Chemical Company.Sulfonium compounds were made using known methods cited in U.S. Pat. No.4,233,421 (Worm), i.e. U.S. Pat. No. 2,807,648 (Pitt), G. H. Wiegard, etal., "Synthesis and Reactions of Triarylsulfonium Halides", J. Org.Chem. 33, 2671-75 (1968), K. Ohkubo et al., J. Org. Chem. 36 3149-55(1971) and U.S. Pat. No. 4,120,866 (Winkler). Bis(benzyldiphenylphosphine) iminium chloride was made according to the proceduredescribed in European Patent Application No. 0182299A2.

EXAMPLES 1-15

The following examples illustrate the use of organo-onium vulcanizationaccelerators in the invention. The ingredients used in each compositionwere compounded on a two roll mill using standard methods. Theorgano-onium vulcanization accelerators are available commercially fromthe sources noted above or were prepared according to known methodsdescribed above. The polyhydroxy crosslinking agent, bisphenol AF,calcium hydroxide and tetramethylenesulfone (TMS) are commerciallyavailable. Magnesium oxide is available as Maglite D™, and carbon blackis available as Thermax MT™, ASTM N990.

The compounded gumstocks were evaluated for cure rheologycharacteristics in accordance with the methods described above, and insome runs, samples were press cured and post cured and post curephysical properties were obtained. The compositions of the compoundedgums, cure rheology characteristics and post cure physical propertiesare summarized in Tables III through VI. As these tables show, thecompositions used in Examples 1-14 had acceptable cure rates andproduced acceptable final cure states as measured by the difference,M_(H) -M_(L). The tables also show Examples 10-13 obtained acceptablepost cure physical properties.

                  TABLE III                                                       ______________________________________                                                     Examples                                                                      1     2      3       4    5                                      ______________________________________                                        Fluoroelastomer A                                                                            100     100    100   100  100                                  Carbon black (phr)                                                                            30      30     30    30   30                                  Ca(OH).sub.2 (phr)                                                                            6       8      8     8    6                                   MgO (phr)       3       3      3     3    3                                   TMS (phr)               1      1     1                                        Bisphenol AF   6.25    6.25   6.25  6.25 6.25                                 (mhr × 10.sup.3)                                                        Benzyltris     4                                                              (dimethylamino)                                                               phosphonium chloride                                                          (mhr × 10.sup.3)                                                        Tributylbenzyl         4                                                      phosphonium                                                                   chloride (mhr × 10.sup.3)                                               Dibutyldiphenyl               4                                               phosphonium                                                                   chloride (mhr × 10.sup.3)                                               Tetraphenylphos-                    4                                         phonium chloride                                                              (mhr × 10.sup.3)                                                        Bis(benzyldiphenyl                       4                                    phosphine)iminium                                                             chloride                                                                      Cure rheology                                                                 M.sub.L (N.m)  1.69    1.81   1.81  1.86 1.86                                 M.sub.H (N.m)  6.67    9.77   9.83  7.85 6.72                                 Min to M.sub.H 12      12     12    12   12                                   t.sub.s 0.2    3.3     3.6    2.2   2.3  5.35                                 t'50           4.3     7.0    3.6   3.6  7.2                                  t'90           5.4     8.5    6.6   4.95 9.4                                  ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                                       Examples                                                       COMPOSITION      6       7       8     9                                      ______________________________________                                        Fluoroelastomer A                                                                              100     100     100   100                                    Carbon black (phr)                                                                              30      30      30    30                                    Ca(OH).sub.2 (phr)                                                                              8       8       8     8                                     MgO (phr)         3       3       3     3                                     TMS (phr)         1       1       1     1                                     Bisphenol AF (mhr × 10.sup.3)                                                            6.25    6.25    6.25  6.25                                   8-Benzyl-1,8,diazobicyclo                                                                      8                                                            [5.4.0]7-undecenium                                                           chloride (mhr × 10.sup.3)                                               Tetrabutylammonium bromide                                                                             4                                                    (mhr × 10.sup.3)                                                        Tetrahexylammonium chloride      4                                            (mhr × 10.sup.3)                                                        Tetraheptylammonium chloride           4                                      (mhr × 10.sup.3)                                                        Cure rheology                                                                 M.sub.L (N.m)    2.26    1.92    1.81  1.67                                   M.sub.H (N.m)    5.98    5.20    7.91  7.03                                   Min to M.sub.H   12      12      12    12                                     t.sub.s 0.2      1.3     3.0     2.4   5.6                                    t'(50)           3.4     4.0     3.5   9.4                                    t'(90)           7.7     6.2     5.7   10.6                                   ______________________________________                                    

                  TABLE V                                                         ______________________________________                                                       EXAMPLES                                                       COMPOSITION      10      11      12    13                                     ______________________________________                                        Fluoroelastomer A                                                                              100     100     100   100                                    Carbon black (phr)                                                                             30      30      30    30                                     Ca(OH).sub.2 (phr)                                                                             8       8       8     8                                      MgO (phr)        3       3       3     3                                      TMS (phr)        1       1       1     1                                      Bisphenol AF (mhr × 10.sup.3)                                                            6.25    6.25    6.25  6.25                                   Tributyl(2-methoxy)                                                                            2.5                                                          propylphosphonium                                                             chloride (mhr × 10.sup.3)                                               Tetrabutylphosphonium    4                                                    chloride (mhr × 10.sup.3)                                               Tetrapentylammonium              4                                            chloride (mhr × 10.sup.3)                                               Tetrabutylammonium                     4                                      chloride (mhr × 10.sup.3)                                               Cure rheology                                                                 M.sub.L (N.m)    1.86    2.03    1.81  1.94                                   M.sub.H (N.m)    8.47    8.47    7.89  6.47                                   Min to M.sub.H   12      12      12    12                                     t.sub.s 0.2      3.3     1.8     2.2   2.05                                   t'(50)           4.4     2.6     3.3   2.9                                    t'(90)           6.4     3.5     5.6   3.9                                    Post Cure, 16 Hr at 232° C.                                            Tensile (MPa)    17.32   13.45   13.12 15.10                                  100% Modulus (MPa)                                                                             7.03    10.58   9.06  9.02                                   Elongation at Break (%)                                                                        189     126     145   156                                    Hardness (Shore A.sub.2)                                                                        77      86      85    83                                    ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                                           EXAMPLES                                                   COMPOSITION          14      15                                               ______________________________________                                        Fluoroelastomer A    100     100                                              Carbon black (phr)   30      30                                               Ca(OH).sub.2 (phr)   8       8                                                MgO (phr)            3       3                                                TMS (phr)            1       1                                                Bisphenol AF (mhr × 10.sup.3)                                                                6.25    6.25                                             Triphenylsulfonium chloride                                                                        4                                                        (mhr × 10.sup.3)                                                        Tritolylsulfonium chloride   4                                                (mhr × 10.sup.3)                                                        Cure rheology                                                                 M.sub.L (N.m)        2.1     1.69                                             M.sub.H (N.m)        3.05    7.23                                             Min to M.sub.H       24      12                                               t.sub.s 0.2          7.9     4.8                                              t'(50)               9.4     6.25                                             t'(90)               12      8.1                                              ______________________________________                                    

EXAMPLES 16-19 and COMPARATIVE EXAMPLES A, B, and C

The following examples illustrate the effectiveness of some of thevarious types of polyhydroxy crosslinking agents included in thisinvention. Examples 16-19 were compounded in the same manner describedin Examples 1-15 except that various polyhydroxy crosslinking agentswere substituted for bisphenol AF. 4,4'-Thiodiphenol and bisphenol Awere obtained from Aldrich Chemical Company.1,1,6,6,-Tetrahydrooctafluorohexanediol is available commercially.Comparative Examples A C were compounded in the same manner described inExamples 1-15 except that in all of the compositions bisphenol A wassubstituted for bisphenol AF, in Comparative Example A the organo-oniumcompound was left out of the composition, in Comparative Example B thepolyhydroxy crosslinking agent was left out of the composition, and inComparative Example C the organo-onium compound was left out of thecomposition and a polyether diol available as Carbowax™ 400 was added tothe composition. The ingredients, amounts of ingredients used, and thecure rheology characteristics are summarized in Tables VII and VIII.

The tables show that the compositions used in Examples 16-19 obtainedacceptable cure rates and final cure states as measured by thedifference, M_(H) -M_(L). However the compositions used in ComparativeExamples A-C, which did not include both an organo-onium compound and apolyhydroxy crosslinking agent did not cure. This illustrates thesynergistic effect of the components of this invention.

                  TABLE VII                                                       ______________________________________                                                       EXAMPLES                                                       COMPOSITION      16      17      18    19                                     ______________________________________                                        Fluoroelastomer A                                                                              100     100     100   100                                    Carbon black (phr)                                                                             30      30      30    30                                     Ca(OH).sub.2 (phr)                                                                             8       6       6     6                                      MgO (phr)        3       3       3     3                                      TMS (phr)        1                                                            Tributyl(2-methoxy)                                                                            2.5     2.5     2.5   4.0                                    propylphosphonium                                                             chloride (mhr × 10.sup.3)                                               Bisphenol AF (mhr × 10.sup.3)                                                            6.25                                                         Bisphenol A (mhr × 10.sup.3)                                                                     6.25                                                 4,4'-Thiodiphenol (mhr × 10.sup.3)                                                                       6.25                                         1,1,6,6-Tetrahydroocta-                12.50                                  fluorohexanediol                                                              (mhr × 10.sup.3)                                                        Cure rheology                                                                 M.sub.L (N.m)    1.86    1.72    1.92  2.09                                   M.sub.H (N.m)    8.47    7.57    5.42  9.04                                   Min to M.sub.H   12      12      12    12                                     t.sub.s 0.2      3.3     2.5     5.2   1.9                                    t'(50)           4.35    3.8     7.3   2.45                                   t'(90)           6.40    6.0     9.7   6.3                                    ______________________________________                                    

                  TABLE VIII                                                      ______________________________________                                                        COMPARATIVE EXAMPLE                                           COMPOSITION       A        B        C                                         ______________________________________                                        Fluoroelastomer A 100      100      100                                       Carbon black (phr)                                                                               30      30       30                                        Ca(OH).sub.2 (phr)                                                                              6        6        6                                         MgO (phr)         3        3        3                                         Bisphenol A (mhr × 10.sup.3)                                                              6.25              6.25                                      Tributyl(2-methoxy)-       4                                                  propylphosphonium                                                             chloride (mhr × 10.sup.3)                                               Carbowax 400 (mhr × 10.sup.3) 5                                         (a polyether diol)                                                            Cure rheology                                                                 M.sub.L (N.m)     1.92     2.37     1.81                                      M.sub.H (N.m)     1.92     2.48     2.14                                      Min to M.sub.H    no cure  no cure  no cure                                   t.sub.s 0.2       --       --       --                                        t'(50)            --       --       --                                        t'(90)            --       --       --                                        ______________________________________                                    

EXAMPLES 20-22

The following examples illustrate the effectiveness of various copolymercompositions on cure rate and final cure state. The compositions werecompounded as described in Examples 1-15, except that a differentcopolymer composition was used in each example. The copolymers used werethe same as those described above and their compositions and propertiesare summarized in Table II. The ingredients used and the cure rheologycharacteristics are summarized in Table IX. The table shows that allcompositions obtained good cure rates and final cure states.

                  TABLE IX                                                        ______________________________________                                                       EXAMPLES                                                       COMPOSITION      20        21      22                                         ______________________________________                                        Fluoroelastomer A                                                                              100                                                          Fluoroelastomer B          100                                                Fluoroelastomer C                  100                                        Carbon black (phr)                                                                             30        30      30                                         Ca(OH).sub.2 (phr)                                                                             8         6       6                                          MgO (phr)        3         3       3                                          Bisphenol AF (mhr × 10.sup.3)                                                            6.25      6.25    6.25                                       Tributyl(2-methoxy)                                                                            4         4       4                                          propylphosphonium                                                             chloride (mhr × 10.sup.3)                                               Cure rheology                                                                 M.sub.L (N.m)    1.75      3.27    .66                                        M.sub.H (N.m)    8.98      10.17   5.20                                       Min to M.sub.H   12        12      12                                         t.sub.s 0.2      2.45      2.1     3.2                                        t'(50)           3.85      3.7     4.1                                        t'(90)           5.80      5.4     6.3                                        ______________________________________                                    

EXAMPLES 22-26

The following examples illustrate the effect addition of one or morediorgano sulfur oxide compounds can have on cure rate. The compositionswere compounded in the same manner as Examples 1-15 except thatdimethylsulfone (DMS) and blends of DMS and TMS were added to thecomposition, and a Tributyl(2-methoxy)propylphosphonium bisphenol AFcomplex (i.e. Tributyl(2-methoxy)propylphosphonium bisphenoxide AF) wasadded to the gum instead of the uncomplexed accelerator. Said complexwas prepared by reacting equimolar amounts of sodium methoxide andbisphenol AF in methanol to form the monosodium salt of bisphenol AF.This monosodium salt was then reacted with an equimolar amount ofTributyl(2-methoxy)propylphosphonium chloride. Sodium chloride formedand precipitated out of solution while the bisphenol-organo-oniumcomplex remained in solution. Cure rheology characteristics weredetermined for all compositions and Mooney scorch values were determinedfor Example 24. The ingredients used in the compositions, the curerheology characteristics, and Mooney scorch values are summarized inTable X. As the table shows, Examples 22 and 23 containing TMS hadsignificantly shorter t'(90) values than Example 21, a similarformulation lacking TMS, and Example 24 containing DMS and had asignificantly shorter t'(90) than Example 21. The table also shows, inExample 25, that a blend of TMS and DMS is also effective in reducingt'(90). The Mooney scorch values from Example 24 indicated that thecomposition did not undergo an increase in the viscosity when heatedbelow its cure temperature, i.e., the composition had low scorch.

                  TABLE XI                                                        ______________________________________                                        COMPOSITION  22      23      24    25    26                                   ______________________________________                                        Fluoroelastomer D                                                                          100     100     100   100   100                                  Carbon block (phr)                                                                         30      30      30    30    30                                   Ca(OH).sub.2 (phr)                                                                         6       6       6     6     6                                    MgO (phr)    3       3       3     3     3                                    Bisphenol AF 3.75    3.75    3.75  3.75  3.75                                 (mhr × 10.sup.3)                                                        Tributyl(2-methoxy)-                                                                       2.5     2.5     2.5   2.5   2.5                                  propylphosphonium-                                                            bisphenoxide AF                                                               (mhr × 10.sup.3)                                                        TMS (phr)            0.5     1.0         0.5                                  DMS (phr)                          1.0   0.5                                  Cure rheology                                                                 M.sub.L (N.m)                                                                              1.69    1.59    1.46  1.46  1.41                                 M.sub.H (N.m)                                                                              9.04    9.49    9.26  9.49  9.60                                 Min to M.sub.H                                                                             12      12      12    12    12                                   t.sub.s 0.2  7.8     5.4     4.5   3.8   3.2                                  t'50         10.2    7.55    6.75  5.25  4.4                                  t'90         11.5    8.4     7.75  6.1   5.5                                  Mooney Scorch                                                                 (MS + 1 @ 121° C.)                                                     Minimum torque (N.m)               3.15                                       N.m rise in 25 min.                0.17                                       ______________________________________                                    

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention.

What is claimed is:
 1. A process of curing an elastomeric compositioncomprising the steps of:(A) providing a mixture of(i) saturatedelastomer gum consisting essentially of repeating interpolymerized unitsderived from vinylidene fluoride, tetrafluorethylene, andcopolymerizable hydrocarbon olefin, and (ii) 0.3 to 10 millimoles ofpolyhydroxy compound per one hundred grams of said gum, (iii) 0.2 to 10millimoles of organo-onium compound per one hundred grams of said gum,and (iv) acid acceptor,except when said gum is derived from vinylidenefluoride, tetrafluoroethylene and propylene, and said polyhydroxycompound is hexafluoroisopropylidene-bis-(4-hydroxybenzene), and saidorgano-onium compound is a phosphonium compound, when said organo-oniumcompound is other than benzyltriphenylphosphonium chloride, (B) shapingsaid mixture, and (C) curing the resulting shaped article.
 2. Theprocess of claim 1 wherein said organo-onium compound is selected fromthe group consisting of quaternary organo-onium compounds sulfoniumcompounds, and mixtures thereof.
 3. The process of claim 2 wherein saidquaternary organo-onium compound is selected from the group consistingof ammonium, arsonium, stibonium, phosphonium, amino-phosphonium,phosphorane, and iminium compounds.
 4. The process of claim 1 whereinsaid mixture further comprises diorgano sulfur oxide compound.
 5. Theprocess of claim 4 wherein said diorgano sulfur oxide compound ispresent at a level of 0.01 to 5 phr.
 6. The process of claim 4 whereinsaid diorgano sulfur oxide compound is selected from the groupconsisting of dimethylsulfone, tetramethylenesulfone, or blends thereof.7. The process of claim 1 wherein said copolymer comprises about 2 to 90mole percent vinylidene fluoride, 5 to 65 mole percenttetrafluoroethylene, and 5 to 45 mole percent hydrocarbon olefin.
 8. Theprocess of claim 7 wherein said hydrocarbon olefin is propylene.
 9. Theprocess of claim 7 wherein said copolymer comprises 2 to 65 mole percentvinylidene fluoride, 20 to 60 mole percent tetrafluoroethylene, and 10to 50 mole percent hydrocarbon olefin.
 10. The process of claim 1wherein said polyhydroxy compound is an aromatic polyhydroxy compound.11. The process of claim 10 wherein said aromatic polyhydroxy compoundhas the general formula ##STR11## wherein A is selected from the groupconsisting of divalent aliphatic, cycloaliphatic, and aromatic radicalsof 1 to 13 carbon atoms, thio, oxy, carbonyl, sulfinyl, and sulfonylradicals, n is 1 or 2, and x is 0 or
 1. 12. The process of claim 11wherein said aromatic polyhydroxy compound is isopropylidene-bis(4-hydroxybenzene) or hexafluoroisopropylidene-bis(4-hydroxybenzene).13. The process of claim 3 wherein said ammonium, phosphonium,stibonium, and arsonium compounds have the formula ##STR12## where Q isselected from the groups consisting of nitrogen, phosphorous, arsenic,and antimony, X is an anion, n is equal to the valence of the anion X,and R², R³, R⁴ and R⁵ are selected from the group of radicals consistingof alkyl, aryl, alkenyl, and combinations thereof, and any pair of saidR groups can be connected with each other and the Q atom to form aheterocyclic ring.
 14. The process of claim 13 wherein three of thegroups R², R³, R⁴ and R⁵ are butyl, the remaining R group is allyl or2-methoxypropyl, Q is phosphorous, n is one and X is bisphenoxide AF.15. The process of claim 13 wherein at least one of the groups R², R³,R⁴ or R⁵ is selected from the group of radicals consisting of alkyl andalkenyl radicals.
 16. The process of claim 3 wherein saidamino-phosphonium compound is selected from the group consisting ofcompounds having the following formulas:

    [P(NR.sup.6 R.sup.7).sub.n R.sup.8.sub.4-n ].sub.m.sup.+ Y.sup.-m, or

    R.sup.9 [P(NR.sup.6 R.sup.7).sub.r R.sup.8.sub.3-r ].sub.2.sup.+ pY.sup.-m

wherein N is nitrogen, P is phosphorous, R⁶, R⁷ and R⁸ are selected fromthe group consisting of alkyl, cycloalkyl, aryl, aralkyl, oxyalkyl andpoly(oxyalkyl) groups with a free or etherified terminal OH function, R⁹is selected from the group consisting of bivalent alkylene, arylene andoxyalkylene radicals, n is a whole number between 1 and 4, r is a wholenumber between 1 and 3, m is a whole number between 1 and 3, Y is ananion of valency m, p is a coefficient such that m times p is
 2. 17. Theprocess of claim 3 wherein said phosphorane compound has the formula##STR13## where Ar ia aryl, and R¹⁰ and R¹¹ are selected from the groupconsisting of (1) separate groups selected individually from (a)hydrogen, methyl, ethyl, propyl, and one to six carbon atom carbalkoxyin the case of R¹⁰ and (b) one to six carbon atom carbalkoxy, cyano, and--CONH₂ in the case of R¹⁰ ; and (2) a single group which together withthe carbon atom to which the single group is attached form a cyclicgroup selected from ##STR14##
 18. The process of claim 3 wherein saidiminium compound has the formula: ##STR15## wherein R¹³, R¹⁴ and R¹⁵ canbe the same or different and can be selected from the group consistingof aryl, 1 to 20 carbon atom alkyl, 3 to 8 carbon atom cycloalkyl, 7 to20 carbon atom aralkyl groups, X is an anion, and c is a number equal tothe valence of X.
 19. The process of claim 2 wherein said sulfoniumcompound has the formula: ##STR16## wherein (a) R¹⁸, R¹⁹, and R²⁰ groupscan be the same or different, at least one of said groups is aromatic,and said groups can be selected from the group consisting of aromaticradicals having 4 to 20 carbon atoms or alkyl radicals having 1 to 20carbon atoms.(b) Z is selected from the group consisting of oxygen,sulfur, >S═O, >C═O, ##STR17## where R²¹ is aryl or acyl, acarbon-to-carbon bond, and ##STR18## where R²² and R²³ are selected fromthe group consisting of hydrogen, alkyl radicals having 1 to 4 carbonatoms, and alkenyl radicals having 2 to 4 carbon atoms, (c) n is zero or1, (d) X is an anion, and (e) a is the valence of X.
 20. The process ofclaim 1 wherein said copolymer is a copolymer derived from 30 to 36 molepercent vinylidene fluoride, 41 to 45 mole percent tetrafluoroethylene,and 19 to 28 mole percent propylene, said polyhydroxy compound ishexafluoroisopropylidene-bis-(4-hydroxybenzene) and said organo-oniumcompound is tributyl (2-methoxy)propylphosphonium chloride.
 21. Theprocess of claim 20 wherein said polyhydroxy compound isisopropylidene-bis(4-hydroxybenzene) instead ofhexafluoroisopropylidene-bis (4-hydroxybenzene).
 22. The process ofclaim 1 wherein said organo-onium compound is selected from the groupconsisting of tritolylsulfonium chloride, tetrabutylphosphoniumchloride, tetrabutylammonium chloride, tetrabutylammonium bromide,tributyl (2-methoxy)propylphosphonium chloride, tetrahexylammoniumchloride, tetraheptylammonium chloride, 8-benzyl-1,8,diazobicyclo[5.4.0]7-undecenium chloride, tributylbenzylphosphoniumchloride, dibutyldiphenylphosphonium chloride, tetraphenylphosphoniumchloride, benzyltris(dimethylamino)phosphonium chloride,tetrapentylammonium chloride, and bis(benzyldiphenylphosphine)iminiumchloride.